Ankle osteoarthritis (OA) is a debilitating and mobility limiting condition. It can commonly stem from the result of a traumatic injury ? such trauma has a high prevalence in military service. If cartilage is not severely damaged in that trauma, the stability and alignment of the joint may be. Over time, an unstable or misaligned ankle joint can experience abnormal rates of cartilage wear and tear due to aberrant kinematics. While OA may take decades to develop, the resulting arthritic state from this trauma will ultimately require ankle replacement or fusion, consequences with a tremendous financial burden and quality of life impact. With regards to alignment, particularly in the coronal plane, current clinical diagnosis relies on static X- ray of the ankle joint. Static images may not indicate dynamic misalignment during gait. Further, the effect of wedged insoles, a potential conservative treatment, on the restoration of ankle function is undocumented. This proposal aims to use biplane fluoroscopy, an X-ray based dynamic imaging approach, to measure ankle kinematics in OA subjects (with varus, neutral and valgus ankle alignment) and controls. With this method, tibio-talar kinematics during gait can be measured. Furthermore, subjects classified as neutral from their static radiograph, but that exhibit ankle varus or valgus alignment during gait, will be identified. Improving the accuracy of a diagnostic outcome provides a patient group with additional avenues for treatment. We will investigate correlations between our 3D kinematics and clinical 2D imaging ? to the benefit of clinical diagnostics. We will also be able to measure the effect of wedged insoles on the restoration of ankle function. With this in mind, the following aims and methodology are proposed. Specific Aim 1: To investigate ankle kinematics in controls and subjects with OA. In support of Specific Aim 1, 90 ankle OA subjects will be recruited (30 each of varus, neutral or valgus aligned ankles). We will also recruit 20 control subjects. Subjects will receive CT scans of their feet to quantify bone geometry (a step necessary for biplane fluoroscopy). Subjects will then be imaged in the biplane system during gait trials and while wearing neutral study shoes. This will yield tibio-talar kinematics during gait for these populations. Specific Aim 2: To identify dynamically misaligned ankles in OA subjects who are currently classified as neutrally aligned using static analysis. We will compare the static X-ray and the gait kinematics of OA subjects, particularly those with clinically determined neutral alignment. We will determine what proportion of neutral OA subjects actually exhibit misalignment during gait and are thus improperly categorized. We will also re-create 2D clinical X-ray views from our 3D data in an attempt to translate our improvement (with 3D fluoroscopy) to more accurately classify alignment to clinical 2D diagnostics. Specific Aim 3: To evaluate the potential of lateral or medial wedging to restore alignment in misaligned ankle OA subjects. OA subjects will be imaged wearing shoes with wedged insoles which correspond to their type of misalignment. Neutral OA subjects, who demonstrate misalignment during gait, will be recalled for a wedged insole session. This yields conservative treatment kinematics. This study will generate baseline data describing the kinematics of control and ankle OA subjects. This data is not currently available in the literature, and represents a novel contribution to the field. Second, this proposal determines how accurate current 2D X-ray methods are at detecting dynamic misalignment. This information can inform clinicians about the accuracy of their diagnostic tools, and may lead to improvements. Third, this proposal will generate data to evaluate the utility of wedged insoles for the conservative management of ankle misalignment. In Summary, this study has immediate impact potential on the diagnosis and treatment of ankle OA. Last, there are numerous additional avenues of classification, diagnostic, and preventative research for the benefit of the veterans which will stem from this Career Development Award.